If you want HV, try the Impulse lipos. I have a 3s 3200mah pack and it's lower profile than a 6c pack.
http://www.hobbypeople.net/gallery/182373.asp
I'm assuming you want 8s? Higher?
http://www.hobbypeople.net/gallery/182374.asp
To me, for hight restrictions the Impulse packs have the skinniest cells available.